Spontaneous Intracranial Hypotension
By Diane Wirz, MD, Associated Neurologists, Danbury, CT.
Ellen is a 45-year-old woman who woke up one day with a severe headache. Headaches were new for her. She had no history of headaches in the past nor did she have a family history of headaches. Yet since that day, Ellen has had a daily headache.
Ellen felt the pain throughout her entire head, but also noticed that it got significantly better when she was lying down. She described the headache's severity as a 10 out of 10. Other than the headache, she felt fine. She didn't have any fever, rashes, joint pains or other symptoms. She saw her internist, who ordered a CT scan, which was normal. She was then referred to a neurologist with an interest in headache.
Ellen's neurological exam was also normal, but the neurologist was quite impressed by how much better Ellen looked and felt when she lay down. The neurologist ordered an MRI scan with contrast, which showed that Ellen's meninges (the coverings around the brain) were brightly enhanced (i.e., highlighted) with the contrast. Ellen was diagnosed with spontaneous intracranial hypotension.
A headache that worsens when a patient is upright and gets better when lying down is a well-recognized complication of a lumbar puncture (spinal tap). However, when this type of headache occurs spontaneously, it is known as spontaneous intracranial hypotension.
Spontaneous intracranial hypotension is caused by a leak of the fluid that surrounds the brain and the spinal cord (the cerebrospinal fluid). Although the body is always making spinal fluid, in this case, the body can't keep up with the rate of the leakage. It is the change in the spinal fluid volume that causes the symptoms. The headache is thought to be due to the sinking of the brain with stretching and distortion of its suspending structures. Engorgement of the intracranial veins may also play a role. The headache may be throbbing or non-throbbing. It may be located anywhere in the head and is occasionally one-sided. Other symptoms that may occur include visual blurring, dizziness, memory problems and problems with balance.
Sometimes patients may have a collagen disease that causes the leak. More commonly, however, there is no underlying disease and it is unclear why the leak develops. If the headache begins suddenly, like a thunderclap, a subarachnoid hemorrhage needs to be ruled out. A rare, but serious complication occurs when there is a collection of blood under the dura called a subdural hematoma. Occasionally, these hematomas will need to be removed.
Diagnosis and Prognosis
The diagnosis is suspected from the patient's history and is then confirmed if the meninges are enhanced in an MRI of the brain. It is important to note that a CT scan is usually normal and that the MRI must be done with contrast to show the meningeal enhancement. If there is any concern that the patient may have another problem, a spinal tap may be done. However, the spinal tap itself may make the headache worse.
If the diagnosis of spontaneous intracranial hypotension isn't made, the headache may transform over time into a chronic, lingering daily headache which is no longer worse when upright and better when lying down. If the patient doesn't remember how the headaches began, the correct diagnosis will likely not be made.
Many times, however, the leak seals up and the patient makes a complete recovery, either spontaneously or with conservative management, such as with bed rest, caffeine and steroids. If the patient doesn't improve with conservative measures, tests can be done to pin-point the location of the leak. If the leak is localized, the patient may have an epidural blood patch in the area of the leak. In this procedure, the patient's own blood is injected into the area to seal off the leak. Fortunately, surgery is rarely needed.